In that the iMac displays are some of the best in the industry in a very competitive price (competitive displays cost nearly the same for the display alone).
My 3 monitors have been used for 4 generations of Macs, though. Definitely agree that monitors live longer than the underlying computer.
Compared to 2006's ACD, new monitors have bigger brightness, better saturation, far wider color gamut, better viewing angles, AND double+ the resolution.